Non-Ai 20mm f/3.5 Nikkor-UD AutoThe Non-Ai
Nikkor-UD 20mm f/3.5 featured here was Introduced in November, 1967, the concept
of optical construction of the lens was entirely new during that era. The lens consists
of 11 elements in 9 groups, with back focus 1.87 times longer than the focal length.
Thus, the lens can be mounted on the camera with the mirror in normal viewing position.
(There is no need to lock up the mirror.as with the RF converted a F-mount 2.1
cm f/4 Nikkor-O).

Unlike the
21mm f/4.0 Nikkor-O that was designed
to used by both rangefinder and reflex SLRs, the old RF lens needs an external finder
for picture composing and the reflex version need a Nikon body that able to mirror
lock up feature to operate. Similarly, those applicable Nikon SLRs also require the
external finder for picture framing. Most of the time, where you can only make use
of the lens' depth of field scales and distance index engraved on the lens barrel/aperture
ring to pre-focus while you shoot. However, with its optical nature where extensive
depth of field can generate when lens diaphragm is closed down slightly, it should
cover a wide range of distances. This is one good advantage of the extremely short
focal length which provides profound depth of field and applied well for that old
Nikkor 21mm RF converted ultrawide lens.

Come to think
of it, Nikon engineers did a commentary good job with this revised 20mm ultrawide
which was designed specifically with Nikon reflex SLRs, the reflex-native 20mm replaced
the older version which requires so much time to setup to use and it eliminated the
need for mirror lock with any Nikon reflex bodies available that time. On the other
hand, the lens was also being designed with a very practical optical formual where
common optical abberations such as coma is minimized, thus enabling the lens provides
sharp images with good contrast across all its aperture settings. It can also close
focus down to 1 ft. and has an optical design of 11 elements in 9 groups (most believed
the 'UD' designation was refeering to the 11 lens elements in its design).

Despite its relatively
slow maximum aperture, the lens has an unusual large filter attachment size of 72mm.
This old Nikkor lens was famed for its equal distribution of brightness in the edge
areas of the image field that facilitates easy viewing and focusing over the entire
focusing screen. Both the aperture and focusing rings are deeply ribbed (the familiar
Nikon rubberized grip was not introduced yet). It finishes in black with only the
lens mounting ring is chrome finished.

Credit: Mr. Bob Hammond where he wrote" " ..Thought I
would send along these photos of a lens hood I have. I believe it is for the Nikkor
20mm F3.5 (UD?), but I use it on a 28mm F4 PC Nikkor. Hope these are of some use
to you on your site...".

Like other Nikkor Auto lenses, the UD Auto features an automatic aperture diaphragm
and a meter coupling prong. Some early versions uses "Nippon Kogaku while later
models reverted back to "Nikon" which give an estimation of its production
stage. With exaggerated perspective, this super wideangle lens is quite effective
in reproducing various subject matters with striking visual effect. The lens was
quite popular in many applications especially suited for architectural photography
and for shooting interiors in confined areas. The lens pictured above looks more
like a Ai-converted Nikkor with an modified Ai lens coupling system. The lens was
eventually being phased out and replaced with a Non-Ai Nikkor 20mm f4.0 which strangely has
a slower lens speed of f/4.0 in 1974 !

Credit: MCLau®, who has helped to rewrite
some of the content appeared this site. Chuck Hester® who has been helping
me all along with the development of all these Nikon websites;LarsHolst Hansen, 'Hawkeye'
who shares the same passion I have; Ms Rissa, Sales manager
from Nikon Corporation Malaysia for granting permission to use some of the official
content; TedWengelaar,Holland
who
has helped to provide many useful input relating to older Nikkor lenses; Some of the references
on production serial numbers used in this site were extracted from Roland Vink's website; HiuraShinsaku from Nikomat
Club Japan. Lastly,
to all the good people who has contributed their own expeience, resources or kind
enough granted permission to use their images of their respective optic in this site.
It is also a site to remember a long
lost friend
on the Net.Note:certain content and
images appeared in this site were either scanned from official marketing leaflets
& brochures published by Nikon and/or contribution from surfers who claimed originality
of their work for educational purposes. The creator of the site will not be responsible
for may discrepancies arise from such dispute except rectifying them after verification."Nikon", "Nikkormat", "Nippon Kokagu
KK"
& "Nikkor" are registered
tradename of Nikon Corporation Inc., Japan. Site made with an Apple IMac.